When the Republican National Committee (RNC) sent out a recent fundraising letter depicting Senate Minority Leader Harry Reid (D-Nev.) as an obstructionist and criticizing some of his sons’ business practices, one of the few Republicans to criticize the attack was home-state Sen. John Ensign.

“I don’t get involved when the RNC attacks him,” Ensign said in an interview last week with The Hill in his Senate office. But, he added, “I don’t like when you go after family members or whatever. That just defies a principle.”

Ensign’s defense — though limited — testifies to the close bond he has formed with Reid after a tough election campaign against him in 1998. The two senators work in tandem on a range of home-state issues — as closely as any two senators from a split delegation.

But that relationship is certain to be tested by Reid’s elevation to his party’s top Senate leadership post, at a time when the chamber’s Republicans are rolling back Democratic opposition to President Bush’s agenda.

In a sign of the endurance of their close ties, however, Reid has signaled that he will not actively campaign against Ensign, who is up for reelection in 2006. Asked if he would stump against Ensign, Reid responded, “I’ll do anything I can to help Democratic candidates.”

But other sources explained that Reid’s activities will be circumscribed. As Ensign explained, he and Reid have a long-standing agreement not to campaign against each other — although each is free to campaign for the other’s opponent.

“Just like I endorsed the Republican candidate [against Reid in 2004], I expect him to endorse the Democratic candidate,” Ensign said. “We have an agreement not to criticize each other. … He can campaign for the other guy.”

Reid cruised to reelection in 2004 after top-tier candidates such as Rep. Jim Gibbons (R-Nev.) took a pass on the race.

But Democrats are not expected to devote special emphasis to Nevada, despite its status as a swing state, preferring to focus on toppling Republicans in Pennsylvania, Virginia, Rhode Island, Montana and Missouri while making a run at seats in Texas and Arizona and contesting an expected open seat in Tennessee.

“Lots of hard feelings on both sides,” Ensign said.The breakthrough came when Ensign opted not to continue with a recount, even though he believes there were serious flaws in how the election was conducted. “I decided that was not the direction to go,” Ensign said. He said he called Reid and told him that he considered Reid to be his senator and “wished him the best.”

“It was from that conversation that he and I started to develop a relationship,” Ensign said. Afterward, Reid consulted him about some Nevada judicial nominations. As it turned out, Sen. Richard Bryan (D-Nev.) soon decided to retire and Ensign picked up the open seat.

“When I got elected, we actually sat down and came to an agreement that we were going to get along, and we also thought it was important for our staffs to get along,” Ensign said, adding that Reid and Bryan had a “great relationship, but their staffs didn’t get along.”

Now, Ensign says his chief of staff, Scott Bensing, has a close working relationship with Reid’s chief of staff, Susan McCue.

In one of their first acts of collaboration, Reid, a former state gaming commissioner, and Ensign, a former general manager of a casino, worked to move a sports betting bill through the Commerce Committee, with each senator securing pledges of support from members of his own party.

“We learned that we could kind of trust each other a little bit,” Ensign said. This year, Reid and Ensign have co-sponsored legislation dealing with hunting licenses, airport screening, drug courts and American Indian housing. They often issue joint press releases, and liberally share credit with each other for legislative accomplishments.

The two also have worked together on national voter-verification legislation after going through an election race that Ensign called incompetent. “We had Florida before Florida was Florida,” he said, comparing the 1998 race to the 2000 presidential election.

The collaboration also extends to constituent service. Reid and Ensign hold joint early-morning breakfast meetings with Nevada constituents, where they engage in light banter with each other.

But Reid and Ensign’s collaborations can be too close for partisans on both sides. Ensign got flak from his own caucus when he submitted to Bush the name of Leif Reid, one of Reid’s sons, as part of a slate for nomination to a federal judgeship. Ensign eventually withdrew Leif Reid, then 35, from consideration.

During the last election cycle, Ensign’s father, Michael Ensign, chairman of the Mandalay Resort Group, a major gambling enterprise, gave $2,000 to Reid’s campaign.

This year, Ensign said, he is preparing for a tough race that could require him to raise as much as $10 million. He held a fundraiser last week with the National Republican Senatorial Committee. “We’re firing on all cylinders,” he said.